A conventional unclogging device for removing obstructions from drains or the like is disclosed in FIGS. 6 and 7, and generally includes a can 60 in which pressurized air is stored and a nozzle 61 is connected to an end of the can 60. A cylindrical cap 62 is mounted to the can 60 and includes a tube 63 which connected to a distal end of the nozzle 61. A spring 64 is mounted to the tube 63 and biased between the can 60 and a wall connected to the tube 63. When pushing the can 60 upside down and pressing the cap 62 against the drain hole, the user presses the can 60 toward the cap and the nozzle 61 is pressed by the stationary tube 63 so that high pressurized air injects into the drain to remove the obstructions which can be flushed away. The device has not any safety device to prevent children from unintentionally pressing the can 60 and the sudden and high pressurized air could injure the children.
The present invention intends to provide a safety cap used for the unclogging device and the cap can only pressed when the cap is rotated an angle.